Rice husks also called rice hulls are the outermost coverings of rice grains. They protect the rice during the growth. They are separated from the rice grains during the milling process. During the milling process, 78 percent of the paddy grain is rice, and 22 percent is the rice husk. The rice husks have 75% volatile organic matter, and the other 25 % is turned into ash known as rice husk ash (RHA). The RHA have 85 – 90 % amorphous silica. The current demand for amorphous silica has pushed its prices over the roof.
Asia is the world leading rice producing continent with nearly 770 million tons annually.As of 2013, China was the leading country with 203.61 million metric tons, second was India with 159.2 million metric tons, third was Indonesia with 71.28, fourth was Bangladesh with 51.5, Fifth was Vietnam with 44.04, and Thailand the sixth with 63.06 million metric tons. Thailand is the largest exporting country. Rice does well in tropical countries because of the availability of water. It is cultivated by flooding the area after seeding. Basmati, Sticky, and Jasmine are the most common types of rice. Rice plants take 3 – 6 months up to maturity, the short duration ones take 105 -120 days while the long duration ones take up to 150 days.
Recently, we have made a pelletizing test of making pellets from rice husks. Click here to view the testing report.
Rice husks initially used to be seen as waste product and was discarded away, but with time it has been processed as by products with many uses. It is a very useful commodity. Rice husks can be converted into rice husk pellets and used for animal bedding, as a fuel and in the production of cement.
Example of Rice Husk Pellet Mill Production Line
Rice husks are used in rice mills to produce steam for steam engines. It has a high calorie value of 14 MJ/kg. This is equivalent to 35% of diesel oil with a 40.5 MJ/kg caloric value. It can be used for electricity generation, and gasification processes.
Rice husk is used for animal feeding and bedding for pets. The husk has fewer proteins. It can be treated with 12 % NaOH to reduce silica substance to enhance assimilation.
It is used for bedding because it is fire-resistant and does not draw insects. It does not take in feces or urine allowing the animals to remain dry and for easy cleaning. It is soft and comfy unlike sawdust.
Burning rice husks in controlled temperatures generates rice husks ash (RHA). RHA contains amorphous silica that is the basic component of the sand which is mixed with cement. Due to its fine nature, it gives a solid concrete. Amorphous silica is ideal in the production of concrete for marine bridges and nuclear plants. the goes deep into cracks in structures sealing it appropriately. The ash has excellent thermal insulation properties.
Rice husks can be made into pellets with the help of a different machine. Rotary dry drum machine dries the rice husks in large scale to reduce the moisture content. It is then crushed into powder. A ring die pellet machine makes the feeding process easy and fast. It is also good for large quantity production. The rice husk powder is then shaped into even shapes and allowed to cool. Later they are packed with the help of pellet packing material. Flat die pellet machine is recommended for small-scale processes. Rice husk pellets are preferred because of low smoke emission and low amount of ashes. They can be quite convenient in storage and transport and can have multiple purposes.
The first thing to look at is the quantity of pellet production. A ring dies pellet mill machine is recommended for large-scale production. It is efficient and easy to use. The mill that has the warranty, it can return in case of damage. Excellent customer service from the sellers in case of a breakdown or for regular maintenance. It should be a machine that has been widely used meaning it has been tested and proven.